1. Field of the Invention
The present invention relates to a bushing, and more particularly to the structure of the vibration damping bushing for use with a link type suspension system for a vehicle and an automotive vehicle drive axle vibration absorbing stabilizing system.
2. Description of the Prior Art
As is well known, a link type suspension system has a structure in which an axle housing is supported from the vehicle body by pairs of upper and lower links extending toward the axle housing on each side thereof. A pair of shock absorbers and suspension springs is disposed between each side of the axle housing and the vehicle body, thereby damping the vertical vibration of the axle housing with respect to the vehicle body.
The suspension system is expected to adequately damp a sudden change in the acceleration of the axle housing due to horizontal vibration and to be firm enough to impart no unnatural sensation.
The energy absorbing rubber sleeve of the bushing provided at one end of each link serves to protect the suspension system itself as well as satisfy the expectation mentioned above by absorbing small vibrations and sounds using deformation of the bushing rubber sleeve with the cooperation of other shock absorbers.
It is difficult, however, to set the resiliency of the rubber sleeve to a value which sufficiently satisfies the two opposing objectives of adequately smoothing a sudden change in the acceleration and being firm enough to impart to unnatural sensation. Accordingly, when drive torque is applied to the drive wheels and a wind-up of the axle housing produced by the drive reaction is transmitted through links to the bushings, the bushings are not expected to greatly damp the wind-up.
Thus, the prior art suspension system further includes an additional shock absorber to damp the moment occurring in the axle housing due to the wind-up.
However, the provision of the additional shock absorber requires relatively many auxiliary parts, such as fixing members and support members, which increases the amount of the assembling work and brings about a high manufacturing cost. A considerably wide space is additionally required between the axle housing and the vehicle body to prevent interference therebetween. Since the additional shock absorber does not operate in a one to one correspondence with the respective movements of the upper and lower links, its ability to damp vibrations is required to be enhanced by a relatively great amount, which may lead to an increase in the shock absorber friction and therefore passenger compartment noise and a harshness which is an impulsive vibration or sound produced when the vehicle runs over a joint or crack in the road.
Generally, in order to enhance the vibration damping characteristic, rubber material having a high loss factor, such as butyl rubber, can be used for the energy absorbing member which, however, increases its dynamic spring constant in high frequency vibrations and, as a result, passenger compartment noise and drive gear clashing increase, and its durability is impaired due to internal heat produced. This is undesirable from the standpoint of vehicle performance. Where the spring constant of the rubber sleeve in the axial direction of the link is decreased in terms of passenger compartment noise and harshness, the vehicle is susceptible to vibration due to axle housing yaw, which is further promoted due to the reduced loss factor of the rubber sleeve.
The present invention intends to eliminate the above drawbacks and problems.